How do you access a static property within a class method?
- Using this.propertyName
- Using self.propertyName
- Using the class name followed by a dot and the property name
- Using super.propertyName
To access a static property within a class method, you use the class name followed by a dot and the property name. This is because static properties are associated with the class itself, not with instances, so you reference them through the class name.
To iterate over an array's elements using a for...of loop, write for (const element _______ array).
- in
- of
- from
- within
In JavaScript, the correct syntax for iterating over an array using a for...of loop is for (const element of array). The of keyword is used to loop over the values in an iterable object like an array.
Can async functions be used as constructors for new objects?
- Yes
- No
- Only in specific JavaScript engines
- Only with the use of decorators
No, async functions cannot be used as constructors for new objects. Async functions always return a Promise, and using them with the new keyword will result in a TypeError. Constructors should return objects, not Promises.
To handle errors in an async function, you should use a try...catch __________.
- Block
- Clause
- Mechanism
- Statement
To catch errors in an async function, you should use a try...catch statement. This helps in graceful error handling and prevents unhandled promise rejections.
In a Promise, if an error is not caught, it leads to a(n) ________.
- Rejection
- Resolution
- Exception
- Completion
In a Promise, when an error occurs and is not caught, the Promise is rejected. This can lead to unhandled promise rejections, causing issues in the application. Understanding how to handle promise rejections is crucial in asynchronous programming with Promises.
How can you access both the index and value of an array element in a for...of loop?
- for (let [index, value] of array.entries())
- for (let {index, value} of array.entries())
- for (let (index, value) of array.entries())
- for (let index, value of array.entries())
In a for...of loop, you can use the entries() method on the array to access both the index and value. The returned value is an array where the first element is the index and the second element is the value. This destructuring assignment allows easy access to both index and value.
When you extend a class in ES6, what must you do before using this in the constructor?
- Initialize the subclass properties
- Call the super() method
- Import the parent class
- Define a new constructor
In ES6, when extending a class, you must call super() in the constructor of the subclass before using this. The super() call initializes the properties of the parent class.
Given an API response with nested data structures, how would destructuring assignment simplify data extraction and handling?
- Extracting specific data becomes concise and readable
- Data extraction becomes slower
- Destructuring cannot be used with nested data structures
- Destructuring has no impact on data handling
Destructuring assignment in ES6 allows developers to extract specific values from nested data structures, making the code more concise and readable. By specifying the desired variables in the destructuring pattern, developers can directly access the required data, avoiding verbose syntax and improving code maintainability. This feature simplifies the process of working with complex API responses or nested objects, enhancing overall code efficiency and clarity.
When building a web application that requests user data from an API and simultaneously posts data to another service, how can Promises enhance code readability and flow?
- Chaining Promises
- Callback Functions
- Asynchronous Callbacks
- Nested Callbacks
Promises allow for chaining, which enhances code readability. Chained promises provide a more elegant and sequential way of handling asynchronous operations compared to nested callbacks, making the code more readable and maintainable.
What happens if you try to import a named export that doesn't exist in the module?
- It will result in a runtime error.
- It will import a null value.
- It will import an undefined value.
- It will not have any effect, and the code will run without errors.
If you try to import a named export that doesn't exist in the module, it will result in a runtime error. The import statement expects the named export to exist, and an attempt to import a non-existent export will throw an error.